Suspension devices as referred to in the beginning are applied, for instance but not exclusively, in trucks or similar heavy-duty vehicles to decouple the driver cabin, in regard to vibrations and movements, from the vehicle chassis. Due to the fact that the spring constant and damping constant of the spring/damping devices of the chassis in heavy-duty trucks are unavoidably high because of the high vehicle loads and because of high springless masses in the chassis, bumps in the road or also vibrations from axles and the drive train are still transferred in a significant proportion via the axle suspension to the chassis and from there to the driver cabin.
To minimize the transfer of such shocks and vibrations, in accordance with the ergonomics and work safety of the driver, to the driver cabin and thus to the workplace of the driver, suspensions for driver cabins have been developed, were the driver cab, or driver cabin, respectively, is supported at the vehicle chassis through its own suspension system. Such suspension systems for the driver cabin can be designed, due to the lower mass of the driver cabin in comparison to the vehicle, with significantly lower spring constants than the axle suspension, a reason why road bumps, or vibrations of the drive train and axles of the vehicle, respectively, are kept away or isolated significantly better from the workplace of the driver due to such cabin suspension systems.
To limit the side roll motion of the driver cabin in such elastic cabin suspension systems, relative to the vehicle chassis, for instance when driving on slopes and curves, but also for instance in the case of bumps on just one side, suspension devices have been designed where a Watt linkage is positioned between the driver cabin and the chassis. The Watt linkage device achieves hereby that spring deflections between cabin and chassis are essentially linear, so that the degrees of freedom of motion between the cabin and the chassis are reduced to vertical spring deflections by means of the Watt linkage device.
Such a suspension device is known, for instance, through DE 10 2005 043 998 A1. This known suspension device comprises in one embodiment two parallel positioned Watt linkages which make sure that the cabin and the chassis of the truck, in regard to roll motions of the truck around the longitudinal axis, are coupled with each other, while a linear spring deflection motion between cabin and chassis, along the vertical axis in the spring deflection, are unrestrictedly possible.
The largely fixed coupling in regard to the roll motions between the cabin and chassis in this known suspension device, however, offers the advantage that self-contained roll motions of the cabin, relative to the chassis, can be eliminated. However, it is inevitable that the driver cab follows every roll motion which is initiated by the chassis. Hereby, the roll angle of the driver cab is equal in size and often—due to the elasticity in the driver cab mounting and the Watt linkages—also larger than the angle of the roll induction which is initiated by the chassis.
Driving on a curve, driving on a slope, or road bumps on just one side, might cause that the driver cab rolls at least equally, if not even more, than the vehicle chassis. Due to comfort and safety reasons it is, however, desirable to at least reduce or eliminate the sideway roll motion of the driver cab in all drive conditions.